Constrained Condition Usage

I have several problems on building constraint condition from documentation.

- What's the difference between `contact` and `pocket`?
- They all have the way of assign special entity by `[entity_number, copy_index, position]`. Is the position the index of the target in special entity? Or the position should be global index?
- For `pocket`, is `binder_chain` necessary? If necessary, the reason pocket is special is that it is for protein_chain-ligand? If not necessary, then what's the difference between assign contact residues in `contact` or `pocket`?
- To achieve the best performance, should I enable `esm` or not?

The payload names no files or tests; start by reading the documentation for constrained conditions, especially the contact, pocket, binder_chain, entity indexing, and esm questions. Done means the documentation clearly explains these distinctions, parameter semantics, and the performance trade-off around esm.

Written by the indexing model from the issue text.